Bell systems are used on house doors, access barriers and the like; in the present case, they are synonymously also referred to as intercom systems or access control systems. Depending on the object on which the bell system is used, the user will require different functions to be implemented in order to meet his specific requirements. For example, users require that, in addition to a pure bell function by means of which even several parties can be separately and independently informed of a person seeking access, a talk-back function is implemented, a video image is recorded and transmitted, or a preferably backlit house number is displayed.
In order to meet these various requirements, it is known to provide frames of different sizes in which different modules can be inserted in order to implement the desired functions. Camera modules, talk-back modules, single bell modules, symbol display modules, multiple bell modules, number block modules, security access modules and modules which combine several of the cited functions, amongst others, should be mentioned here.
In the present case, systems are to be understood to be a bell system particularly when they do not have an actual bell button but implement at least one of the cited functions.
While this use of modules which can be inserted into the frame can result in a significant reduction in production and storage costs, problems may arise when the bell system is mounted on an object which is situated in an area which is at risk of theft or vandalism or in which acts of sabotage cannot be precluded. In a situation such as this, there is a risk of the modules being removed from the frame and being re-inserted in an inoperative state or being stolen.
In principle, it would be possible to connect the modules in a permanent and fixed manner to the frame after said modules have been inserted, for example by latching said modules into place, in order to prevent theft and sabotage, but permanent connection of this kind again creates problems if the modules have to be replaced, for example due to defects or because the functions required by the user have changed.
It has therefore already been proposed to provide a latching mechanism which fixes the individual modules to the frame using moving latching lugs. The movement of the latching lugs then releases the modules again and is effected in commercially available frames by exciting a monostable electromagnetic actuator, the modules being locked in the stable position of said actuator.
This makes it easier to subsequently replace modules but has proven complicated in terms of initial installation, in particular, because the modules still have to be repeatedly removed from the frame and re-inserted specifically during installation, typically initially for the purpose of checking the connection and for the purpose of adjusting the module arrangements in the frame, etc.
It would be desirable to be able to specify a bell system which ensures a high level of security at low cost yet is simple to assemble.
The object of the present invention is to provide a novel subject matter for industrial use.
The way in which this object is achieved is claimed in independent form. Preferred embodiments can be found in the dependent claims.